1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device that comprises a resistor film consisting of polysilicon formed in an insulating film on a semiconductor substrate.
2. Background Art
FIG. 5 is a sectional view showing a schematic configuration of a conventional integrated circuit that comprises polysilicon resistors. In this drawing, reference numeral 1 is a silicon substrate, i.e. a semiconductor substrate; 2 is an insulating film consisting of a field oxide film or an interlayer insulating film formed on the silicon substrate 1, 3 is a resistor film consisting of polysilicon formed in the insulating film 2; 4A and 4B are terminal wirings of the resistor film 3 formed on the insulating film 2, and connected to the resistor film 3 through connecting portions 5A and 5B.
The integrated circuit comprising a conventional resistor film is constituted as described above, and heat generated in the resistor film 3 is dissipated into the silicon substrate 1 through the insulating film 2 underneath the resistor film 3, but the heat is not sufficiently transferred because the insulating film 2 underneath the resistor film 3 is as thick as about 0.5 μm, thereby raising a problem of low resistance to instantaneous surge electric power.
Specifically, as shown by curve a in FIG. 3 that indicates the result of simulation of the temperature rise of the resistor film 3 in the case where a step electric power of about 3 mW was consumed, a temperature rise per unit power consumption was as large as 2,200 deg./W, in 1 μs showing a large transient heat impedance.
Also, as shown by curve a in FIG. 4 that indicates the result of ESD (electrostatic discharge) simulation of discharge from a 200 pF capacitor, temperature rose rapidly in 700 ns after starting power supply to over 2,000 K, leading to thermal breakdown.
In recent years, since the resistor film 3 is becoming thinner accompanying the size reduction of transistors due to the advancement of micro machining technology, the resistance to surge power tends to further lower.